Visible light-activated photocatalytic coating composition and air purification filter

ABSTRACT

Disclosed is a visible light-activated photocatalytic coating composition comprising a visible light active photocatalytic material and an aqueous solvent.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of the U.S. patent application Ser.No. 15/553,773 filed on Aug. 25, 2017, which is a National Phaseapplication of International Application No. PCT/KR2016/001741 filed onFeb. 23, 2016 which is based upon and claims the benefit of priority toKorean Patent Application No. 10-2015-0027402 filed on Feb. 26, 2015 inthe Korean Intellectual Property Office. The disclosures of theabove-listed applications are hereby incorporated by reference herein intheir entirety.

TECHNICAL FIELD

The present disclosure relates to a visible light-activatedphotocatalytic coating composition and an air purification filter.

BACKGROUND ART

In general, air purification filters have been used for the purpose ofremoving dust, germs and other contaminants in a room air.

Such air purification filters have a porous structure, and contaminantscan be adsorbed and removed, but the adsorbed contaminants are piled upover time, and the air purifying function is deteriorated and the filterhas to be replaced continuously, which is however uneconomical.

Therefore, the life of the filter may be extended by decomposing andremoving the adsorbed contaminants by activating water, oxygen, etc.contained in the air by using a photocatalyst.

However, in order to coat the filter with such photocatalyst, a bindermaterial was required to use, which may clog the pores of the filter orattach to the surface of the photocatalyst, thereby lowering the surfaceactivity of the photocatalyst to light.

In addition, even when an alcohol solvent is used to rapidly coat thephotocatalyst, the surface activity of the photocatalyst may be lowered.

DISCLOSURE Technical Problem

One aspect of the present disclosure is to provide a visiblelight-activated photocatalytic coating composition which can achievevisible light activity performance and excellent photocatalyticefficiency, and quick and easy coating.

Another aspect of the present disclosure is to provide an airpurification filter that can realize excellent air cleaning,deodorization and antibacterial performance for a long period of time.

Technical Solution

In one embodiment of the present disclosure, there is provided a visiblelight-activated photocatalytic coating composition including a visiblelight active photocatalytic material and an aqueous solvent.

The visible light active photocatalytic material may have activityagainst visible light in the wavelength range of about 380 nm to about500 nm.

The visible light active photocatalytic material may include a porousfirst metal oxide; a second metal particle supported on the porous firstmetal oxide, a second metal oxide particle, or both.

The first metal oxide may include at least one selected from titaniumoxide, tungsten oxide, zinc oxide, niobium oxide, and combinationsthereof.

The second metal of the second metal particle and the second metal oxideparticle may include a transition metal, a noble metal, or both.

The second metal may include at least one selected from the groupconsisting of tungsten, chromium, vanadium, molybdenum, copper, iron,cobalt, manganese, nickel, platinum, gold, cerium, cadmium, zinc,magnesium, calcium, strontium, barium, radium, palladium, andcombinations thereof.

The weight ratio of the porous first metal oxide to the sum of thesecond metal particle and the second metal oxide particle contained inthe visible light active photocatalytic material may be about 1:0.001 toabout 1:0.1.

The visible light-activated photocatalytic coating composition may becoated on an activated carbon-containing porous substrate to form aphotocatalytic coating layer for an air purification filter.

The activated carbon-containing porous substrate may be formed byattaching or impregnating an activated carbon to/into the poroussubstrate formed of materials including at least one selected from thegroup consisting of woven or nonwoven fabric made of an organic orinorganic fiber, paper, foam, and combinations thereof.

The visible light active photocatalytic material may be included in theamount of about 4% to about 10% by weight.

The aqueous solvent may be included in the amount of about 90% to about96% by weight.

The aqueous solvent may be water.

The visible light active photocatalytic material may be formed intoparticles.

The visible light active photocatalytic material particles may have anaverage diameter of about 30 nm to about 500 nm.

The composition may not include an alcohol and a binder material.

In another embodiment of the present disclosure, there is provided anair purification filter including a photocatalytic coating layer formedfrom the visible light-activated photocatalytic coating composition.

The air purification filter may not include an alcohol and a bindermaterial.

The air purification filter may further include an activatedcarbon-containing porous substrate, and the photocatalytic coating layermay be coated on the activated carbon-containing porous substrate.

The activated carbon-containing porous substrate may contain about 20%to about 80% by weight of activated carbon.

The activated carbon-containing porous substrate may have a thickness ofabout 0.5 mm to about 3.0 mm.

Advantageous Effects

The visible light-activated photocatalytic coating composition canrealize visible light activity performance and excellent photocatalyticefficiency, and quick and easy coating.

BEST MODE

Hereinafter, embodiments of the present disclosure will be described indetail. The embodiments are for illustrative purpose only, but not forlimiting the present disclosure. The present disclosure is only definedby the scope of the following claims.

In one embodiment of the present disclosure, there is provided a visiblelight-activated photocatalytic coating composition including a visiblelight active photocatalytic material and an aqueous solvent.

The photocatalytic material refers to a substance capable of aircleaning, deodorizing, and antibacterializing by generating electronsand holes, such as, superoxide anions or hydroxyl radicals, generatedfrom the energy obtained by absorbing light.

Such photocatalytic material usually includes an ultravioletray-activated photocatalyst, for example, an ultraviolet ray-activatedphotocatalyst made of titanium oxide. However, since the efficiency ofthe photocatalytic material is very low by an indoor light source, aseparate light source for irradiating ultraviolet rays is required.

Further, in order to coat the filter with such photocatalytic material,a binder material is required to use, which may clog the pores of thefilter or attach to the surface of the photocatalyst, thereby loweringthe surface activity of the photocatalyst to light.

Further, when an alcohol solvent is used to quickly absorb and dry acoating composition containing the photocatalytic material, the solutesuch as photocatalyst may be precipitated more quickly and thedispersibility may be lowered, and the components such as platinum whichmay be contained in the photocatalytic material in the alcohol solventmay cause an alcohol decomposition reaction, resulting in low storagestability.

In one embodiment, the photocatalytic material including a visible lightactive photocatalytic material can be activated not only by ultravioletrays but also by visible light to realize the visible light activeperformance, and, therefore, the photocatalytic efficiency can beimproved to a high level without a separate light source supply unit ina room. At the same time, it is possible to effectively prevent theclogging of the pores of the filter including the aqueous solvent andprevent the deterioration of the surface activity of the photocatalyst,thereby prolonging the life of the product, and the precipitation rateof the photocatalytic material can be further reduced to improve thedispersibility. Further, it is possible to prevent the reaction betweenthe photocatalytic material and the solvent, thereby providing long-termuniform performance, excellent storage stability, and excellent economicefficiency.

The visible light active photocatalytic material may be prepared to haveactivity for visible light in the wavelength range of about 380 nm toabout 500 nm, and, for example, may exhibit an absorbance of about 20%for visible light at a wavelength of about 400 nm, and an absorbance ofabout 10% for visible light at a wavelength of about 500 nm.

Thus, since the visible light active photocatalytic material is activewithin the wavelength range of the visible light region, the visiblelight active photocatalytic material can sufficiently generate electronsand holes by means of an indoor light source without a separate lightsource supply unit for irradiating ultraviolet light, thereby realizingexcellent photocatalytic efficiency.

The visible light active photocatalytic material may include a porousfirst metal oxide; and a second metal particle supported on the porousfirst metal oxide, a second metal oxide particle, or both.

The porous first metal oxide may be formed into a spherical, plate orspindle-like particle as a support by, for example, a sol-gel method ora hydrothermal method.

For example, the second metal particles or the second metal oxideparticles may be supported on the porous first metal oxide by aphoto-deposition method, but the present disclosure is not limitedthereto.

The first metal oxide may, for example, include at least one selectedfrom titanium oxide, tungsten oxide, zinc oxide, niobium oxide, andcombinations thereof. Specifically, the first metal oxide may includetungsten oxide to further improve the visible light activityperformance.

The first metal oxide particles may have an average diameter of, forexample, about 30 nm to about 100 nm.

The second metal of the second metal particles and the second metaloxide may use, for example, a metal which can impart activity to visiblelight and may include transition metals, noble metals or both. That is,the second metal particles and the second metal oxide may include atleast one selected from the group consisting of transition metals, noblemetals or oxides thereof, and combinations thereof.

In addition, the second metal may include, for example, at least oneselected from the group consisting of tungsten, chromium, vanadium,molybdenum, copper, iron, cobalt, manganese, nickel, platinum, gold,cerium, cadmium, zinc, magnesium, calcium, strontium, barium, radium,palladium, and combinations thereof. Specifically, the second metal mayinclude at least one selected from the group consisting of platinum,copper, gold, silver, zinc, palladium, and combinations thereof torealize excellent visible light activity performance.

In particular, the first metal oxide may comprise tungsten oxide and thesecond metal may comprise platinum, thereby absorbing visible light to ahigher level to effectively enhance photocatalytic efficiency forvisible light.

In one embodiment of the present disclosure, the weight ratio of theporous first metal oxide to the sum of the second metal particle and thesecond metal oxide particle contained in the visible light activephotocatalytic material may be about 1:0.001 to about 1:0.1. Within theabove range of content, the first metal oxide sufficiently generateselectrons and holes by visible light and sufficiently prevents therecombination of electrons and holes generated by the second metalparticles or the second metal oxide particles to effectively improvephotocatalytic activity efficiency.

The total sum of the second metal particles and the second metal oxideparticles may refer to a single sum, that is, the total sum of thesecond metal particles or the sum of the second metal oxide particles,and when both of them are included, it refers to a total sum of thesecond metal particles and the second metal oxide particles.

For example, the total content of the second metal particles and thesecond metal oxide particles included in the visible light activephotocatalytic material may be about 0.1% to about 10% by weight. Inthis embodiment, the content of the porous first metal oxides may beabout 90% to about 99.9% by weight. Within this range of content,excellent photocatalytic activity can be provided.

Specifically, when the content of the first porous metal oxides isgreater than about 99.9% by weight, electrons and holes generated byvisible light may easily recombine with each other, and therebydifficult to separate and can exhibit unsufficient photocatalyticactivity, whereas when the content is less than about 90% by weight, thenumber of electrons transferred from the porous first metal oxides maynot be sufficiently secured, which may in turn lower the photocatalyticactivity, and the exposed area of the first metal oxides to light may bereduced, thereby deteriorating photocatalytic performance.

In addition, some of the porous first metal oxides may be agglomeratedtogether to form a cluster.

Depending on the shape of the first metal oxides, the visible lightactive photocatalytic material may be formed into particles.

The visible light active photocatalytic material particles may have anaverage diameter of about 30 nm to about 500 nm, and particularly about30 nm to about 200 nm.

Within the above range of average diameter, when the visiblelight-activated photocatalytic coating composition is coated on theporous substrate, the visible light active photocatalytic material maybe more uniformly dispersed, and the porous substrate may penetrate theporous substrate more quickly, and thereby excellent dispersibility andexcellent adhesion can be realized. In addition, it is possible toensure sufficient air cleaning and antifungal function by securing anexposed area for visible light.

Further, the first metal oxide may have a specific surface area of about50 m²/g to about 500 m²/g. Within the above high level of specificsurface area, the first metal oxide can be effectively exposed to alight source such as visible light and the porosity can be formed at anappropriate level to sufficiently support the second metal particles andthe second metal oxide particles.

In one embodiment, the visible light-activated photocatalytic coatingcomposition may comprise from about 4% to about 10% by weight of thevisible light active photocatalytic material. Within the above contentrange, the coating composition can achieve sufficiently good aircleaning, deodorization and antibacterial performance even with visiblelight, without excessively increasing the cost.

Further, the visible light-activated photocatalytic coating compositionmay include about 90% to about 96% by weight of the aqueous solvent.Within the above range of content, the coating composition canappropriately disperse the visible light active photocatalytic materialand the coating on the porous substrate, for example, the porous filtercan be facilitated, and quickly absorbed and dried, thereby increasingproduction efficiency.

Specifically, when the content of the aqueous solvent is less than about90%, the visible light active photocatalytic material is difficult todisperse and the visible light-activated photocatalytic coatingcomposition is difficult to coat, so that the uniform performance cannotbe achieved as a whole, and the adhesion may be deteriorated, whereaswhen it is more than about 96%, the content of the visible light activephotocatalytic material is so low that the air cleaning, deodorization,and antibacterial performance may not be sufficient.

The aqueous solvent may be water. For example, the aqueous solvent is asolvent consisting of 100% by weight of water, which may include, but isnot limited to, distilled water, ionized water, or both.

In one embodiment, the visible light-activated photocatalytic coatingcomposition may not comprise an alcohol and a binder material. Thus, theexposed surface area of the visible light active photocatalytic materialis sufficiently included to realize excellent photocatalytic efficiency,and the adsorption and removal performance of harmful substances such asvolatile organic compounds (VOCs) can be effectively improved.

Such a binder material refers to an organic binder or an inorganicbinder including a binder resin known in the art, for example, anacrylic resin, a polyester resin, etc., and specifically includes, butis not limited to, silica sol, alumina sol, zirconia sol, and the like.

In general, toluene has a large molecular weight and is non-polar, butif the exposed surface area is small, adsorption and removal aredifficult.

As described above, the visible light-activated photocatalytic coatingcomposition does not include an alcohol and a binder material, so thatthe exposed surface area of the visible light active photocatalyticmaterial may not be reduced. Specifically, the adsorption of a toxicsubstance such as toluene occurs at a high level, such that an excellentremoval can be achieved.

As described in other embodiment of the present disclosure hereinbelow,the visible light-activated photocatalytic coating composition may becoated on an activated carbon-containing porous substrate to form aphotocatalytic coating layer for an air purification filter, and,accordingly, air cleaning, deodorization or antibacterial effect can beimproved.

The activated carbon may have a very high adsorptivity as a porouscarbonaceous material including micropores.

The photocatalytic coating layer for the air purification filter may beformed, without limitation, by dipping the activated carbon-containingporous substrate in the visible light-activated photocatalytic coatingcomposition, followed by drying, or by spraying the visiblelight-activated photocatalytic coating composition onto the activatedcarbon-containing porous substrate by a spray method.

Thus, the present disclosure is advantageous in that the visiblelight-activated photocatalytic coating composition is applied to aporous substrate containing an activated carbon, thereby realizingexcellent adhesion even without containing a binder material, and beingcapable of being rapidly absorbed and dried without containing analcoholic solvent.

For example, the activated carbon-containing porous substrate may beformed by attaching or impregnating an activated carbon to/into theporous substrate formed of a material including at least one selectedfrom the group consisting of woven or nonwoven fabric made of an organicor inorganic fiber, paper, foam, and combinations thereof.

The method of attaching or impregnating the activated carbon to/into theporous substrate may be performed according to a method known in theart, and, for example, without limitation, may be carried out byimmersing the porous substrate in an activated carbon-containingcomposition and then drying it, or by spraying the activatedcarbon-containing composition onto the porous substrate by a spraymethod.

The activated carbon-containing porous substrate may contain about 20%to about 80% by weight of activated carbon. Within the above range ofcontent, the substrate can sufficiently absorb harmful substances in theair, and can adsorb the visible light-activated photocatalytic coatingcomposition to a high level, without excessively increasing the cost.

The activated carbon-containing porous substrate may further include anadsorbent containing at least one selected from the group consisting ofdiatomaceous earth, zeolite, silica gel, starch, bentonite, alumina, andcombinations thereof.

The activated carbon-containing porous substrate may have a thickness ofabout 0.5 mm to about 3.0 mm Within the above range of thickness, theair cleaning, deodorizing, or antibacterial effect can be exerted to anexcellent level without excessively increasing the thickness of the airpurification filter.

In another aspect of the present disclosure, there is provided an airpurification filter including a photocatalytic coating layer formed fromthe visible light-activated photocatalytic coating composition. Thevisible light-activated photocatalytic coating composition is asdescribed above in one embodiment.

As such, since the air purification filter can realize visible lightactivation performance, the photocatalytic efficiency can be improved toa high level without a separate light source supply unit in a room. Atthe same time, the visible light-activated photocatalytic coatingcomposition can effectively prevent the clogging of the pores of thefilter including the aqueous solvent and prevent the deterioration ofthe surface activity of the photocatalyst, thereby prolonging the lifeof the product, and the precipitation rate of the photocatalyst can befurther reduced to improve the dispersibility. Further, it can preventthe reaction between the photocatalytic material and the solvent,thereby providing long-term uniform performance, excellent storagestability, and excellent economic efficiency.

Specifically, the air purification filter may not include an alcohol anda binder material. As a result, the exposed surface area of the visiblelight active photocatalytic material is not reduced, and the adsorptionof harmful substances such as toluene occurs at a high level, therebyrealizing an excellent removal and realizing excellent dispersibilityand excellent storage stability as described above.

The air purification filter may further include an activatedcarbon-containing porous substrate, and the photocatalytic coating layermay be coated on the activated carbon-containing porous substrate. Forexample, the photocatalytic coating layer may be coated on the entiresurface of the activated carbon-containing porous substrate, that is,coated on both the outer surface exposed to the outside of the surfaceof the activated carbon-containing porous substrate and the innersurface forming the pores therein.

The activated carbon-containing porous substrate may be coated, withoutlimitation, by spraying the visible light-activated photocatalyticcoating composition on the activated carbon-containing porous substrate,or by immersing the activated carbon-containing porous substrate in thevisible light-activated photocatalytic coating composition, followed bydrying. The activated carbon-containing porous substrate is as describedabove in one embodiment.

Thus, the present disclosure is advantageous in that the visiblelight-activated photocatalytic coating composition is applied to aporous substrate containing an activated carbon, thereby realizingexcellent adhesion even without containing a binder material, and beingcapable of being rapidly absorbed and dried without containing analcoholic solvent. Accordingly, when used in an air conditioner, avacuum cleaner, a heater, an air cleaner, etc., the photocatalyticcoating layer is not separated from the activated carbon-containingporous substrate due to the flow of air, so that air cleaning,deodorization or antibacterial effect can be achieved for a long periodof time.

For example, the activated carbon-containing porous substrate may beformed by attaching or impregnating an activated carbon to/into theporous substrate formed of a material including at least one selectedfrom the group consisting of woven or nonwoven fabric made of an organicor inorganic fiber, paper, foam, and combinations thereof. The method ofattaching or impregnating the activated carbon to/into the poroussubstrate may be performed according to a method known in the art, andis not particularly limited.

The activated carbon-containing porous substrate may contain about 20%to about 80% by weight of activated carbon. Within the above range ofcontent, the substrate can sufficiently absorb harmful substances in theair, and can adsorb the visible light-activated photocatalytic coatingcomposition to a high level, without excessively increasing the cost.

The activated carbon-containing porous substrate may further include anadsorbent containing at least one selected from the group consisting ofdiatomaceous earth, zeolite, silica gel, starch, bentonite, alumina, andcombinations thereof.

The activated carbon-containing porous substrate may have a thickness ofabout 0.5 mm to about 3.0 mm Within the above range of thickness, theair cleaning, deodorizing, or antibacterial effect can be exerted to anexcellent level without excessively increasing the thickness of the airpurification filter.

The air purification filter may be formed in a shape known in the art,including, for example, a honeycomb type, a sheet type, a back type, andcombinations thereof.

For example, the honeycomb type may be formed in a honeycomb shape, thesheet type may be formed in a thin plate shape, and the bag type may beformed in an elongated bag shape.

Hereinafter, examples of the present disclosure will be described.However, the following examples are described for illustrative purposesonly, and the present disclosure is not limited to the followingexamples.

EXAMPLES Example 1

Tungsten oxide (WO₃) powder was dispersed into water and then 0.2 partby weight of chloroplatinic acid (H₂PtCl₆) was added based on 100 partsby weight of tungsten oxide (WO₃) to the solution to prepare Pt/WO₃slurry. While stirring the slurry, UV of a UV lamp (20 W) was irradiatedfor about 30 minutes to dope platinum (Pt) particles into the tungstenoxide (WO₃) particles. Thereafter, 10% by weight of a methanol solutionwas added to the slurry containing the tungsten oxide (WO₃) particlesdoped with the platinum (Pt) particles. While stirring the slurry, UV ofa UV lamp (20 W) was irradiated for about 30 minutes to form a visiblelight active photocatalytic material having platinum (Pt) particlessupported on the tungsten oxide (WO₃). The weight ratio of the tungstenoxide to the platinum particles was 1:0.002.

5% by weight of the visible light active photocatalytic material and 95%by weight of water were mixed and stirred to prepare a visiblelight-activated photocatalytic coating composition.

Further, the activated carbon was impregnated into a nonwoven fabrichaving a thickness of 2 mm using a polypropylene fiber material toprepare an activated carbon-containing porous substrate. The activatedcarbon-containing porous substrate contained 60% by weight of theactivated carbon.

Then, the activated carbon-containing porous substrate was immersed inthe visible light-activated photocatalytic coating composition and driedto prepare an air purification filter.

Comparative Example 1 (when an Aqueous Solvent is not Contained and aBinder Material is Contained)

A visible light activated photocatalytic composition and an airpurification filter were prepared in the same manner as in Example 1,except that water was not mixed and stirred, and 5% by weight of avisible light active photocatalytic material, 90% by weight of isopropylalcohol (IPA) and 5% by weight of a TiO₂ sol binder were mixed andstirred.

Evaluation

Toluene Removal Rate

Measurement: The air purification filters in Example 1 and ComparativeExample 1 were installed in a small-sized chamber (ADTEC) of 20 Lvolume, and then 0.2 ppm of toluene-containing air was continuouslysupplied to the chamber at a flow rate of 167 cc/min to allow theventilation to be 0.13 times/hr. LED 20 W module was used as a lightsource. The toluene removal rate was calculated using the followingformula 1 by measuring a concentration of toluene before entering thechamber (hereinafter referred to as a first concentration) and aconcentration of toluene in the air after passing through the chamber(hereinafter referred to as a second concentration). The concentrationswere analyzed by concentrating the volume for 10 L volumes using a DNPH(2,4-dinitrophenylhydrazine) cartridge via HPLC (Agilent). The resultsare shown in Table 1 below.Toluene removal rate (%)=(first concentration−secondconcentration)/(first concentration)×100  [Formula 1]

TABLE 1 Toluene removal rate [%] Ex. 1 83 C. Ex. 1 34

As shown in Table 1 above, it can be clearly seen that the airpurification filter according to Example 1, which was prepared using anaqueous solvent without using a binder material, had a very high tolueneremoval rate of 83%, whereas the air purification filter according toComparative Example 1 using a binder material had a remarkably lowtoluene removal rate of 34%.

The invention claimed is:
 1. An air purification filter comprising: aporous substrate comprising activated carbon, wherein an amount of theactivated carbon ranges from 20% to 80% by weight based on an amount ofthe porous substrate, and the porous substrate is formed by attachingthe activated carbon to or impregnating the activated carbon into amaterial comprising a woven or nonwoven fabric made of an organic fiberor inorganic fiber; and a photocatalytic coating layer formed from avisible light-activated photocatalytic coating composition, wherein thephotocatalytic coating layer is coated on the porous substrate and theactivated carbon, and the visible light-activated photocatalytic coatingcomposition comprises a visible light active photocatalytic material,wherein the visible light active photocatalytic material comprises aporous first metal oxide; and a second metal particle supported on theporous first metal oxide, a second metal oxide particle, or both,wherein the first metal oxide is a tungsten oxide (WO₃) and a secondmetal of the second metal particle and the second metal oxide particleis platinum (Pt), the visible light active photocatalytic material isformed into particles, the visible light-activated photocatalyticcoating composition does not comprise an alcohol and a binder material.2. The air purification filter of claim 1, wherein the photocatalyticcoating layer is coated on the porous substrate and the activated carbonby immersing the porous substrate and the activated carbon in thevisible light-activated photocatalytic coating composition.
 3. The airpurification filter of claim 1, wherein an amount of the visible lightactive photocatalytic material ranges from 4% to 10% by weight based onan amount of the visible light-activated photocatalytic coatingcomposition.
 4. The air purification filter of claim 1, wherein thevisible light-activated photocatalytic coating composition comprises anaqueous solvent.
 5. The air purification filter of claim 1, wherein thevisible light active photocatalytic material has an activity againstvisible light in the wavelength range of 380 nm to 500 nm.
 6. The airpurification filter of claim 1, wherein the weight ratio of the porousfirst metal oxide to the sum of the second metal particle and the secondmetal oxide particle contained in the visible light activephotocatalytic material is 1:0.001 to 1:0.1.
 7. The air purificationfilter of claim 1, wherein an amount of the aqueous solvent ranges from90% to 96% by weight based on an amount of the visible light-activatedphotocatalytic coating composition.
 8. The air purification filter ofclaim 4, wherein the aqueous solvent is water.
 9. The air purificationfilter of claim 4, wherein the aqueous solvent is 100% by weight ofwater.
 10. The air purification filter of claim 1, wherein the visiblelight active photocatalytic material particle has an average diameterfrom 30 nm to 500 nm.
 11. The air purification filter of claim 1,wherein the porous substrate comprising activated carbon has a thicknessranging from 0.5 mm to 3.0 mm.